KR20170032434A - Electric actuator - Google Patents

Abstract

The electric actuator 10 is configured such that the nut 52 screwed with the sliding screw shaft 18 is displaced along the axial direction under the action of the motor 12 and the sliding screw shaft 18 is composed of a light metal or a light metal alloy do. Like carbon films 50, 50 are formed on at least one of the portions located at least three turns from the starting end in the axial direction of the threaded portion 58 of the nut 52 and the threaded portion 48 of the sliding screw shaft 18, 60 are formed.

Description

ELECTRIC ACTUATOR

The present invention relates to an electric actuator in which a nut screwed to the sliding screw shaft is displaced along the axial direction of a sliding screw shaft by rotating the sliding screw shaft under the action of a motor.

The electric actuator includes a feed screw shaft rotating under the action of a motor and a nut screwed into the feed screw shaft. In this feed screw shaft, a ball screw shaft or a sliding screw shaft is generally used. From the viewpoint of endurance, the ball screw shaft is made of heat-treated quenched steel, the sliding screw shaft is made of iron and plated with nickel or hard chrome, and the nut screwed to the sliding screw shaft is made of copper or resin .

For example, in Japanese Patent Laid-Open Publication No. 2014-47884, in an electric actuator having a ball screw shaft, a diamond-like carbon (DLC) film is formed on a rod seal member, There has been proposed a technical idea for improving the wear resistance as well as performing a smooth operation by reducing the friction coefficient of the seal member.

However, in the case of using the ball screw shaft described in JP-A-2014-47884, the nut screwed to the ball screw shaft is relatively large, and the electric actuator becomes large, and the operation sound can be increased by circulation of the steel ball . On the other hand, in the case of using the sliding screw shaft, it is possible to relatively reduce the nut and the operating noise that are screwed to the sliding screw shaft, but there is a problem that wear is easier than the ball screw shaft. It is also conceivable to reduce the motor load (inertia force) by constructing the sliding screw shaft and the nut with a light metal such as aluminum or a light metal alloy such as an aluminum alloy in order to reduce the weight and size of the electric actuator. In this case, And the nut is more susceptible to wear. Further, electric actuators used in hospitals and the like are expected to have a further reduced noise level.

In view of the above problems, the inventors of the present application have carried out a stress analysis of a sliding screw shaft and a nut at the time of driving an electric actuator, and have found that from the starting end (end) of the axial direction to the third The stress is concentrated on the portion located in the range of < RTI ID = 0.0 > Further, by forming a diamond-like carbon film on at least one of the portion located in the range of the screw thread of the nut and the thread ridge of the feed screw shaft, the sliding sound (A state close to silence).

An object of the present invention is to provide an electric actuator capable of improving the wear resistance and durability of a sliding screw shaft and a nut as well as achieving weight reduction, miniaturization and low noise.

An electric actuator according to the present invention is an electric actuator in which a nut screwed on a sliding screw shaft is displaced along the axial direction of the sliding screw shaft by rotating a sliding screw shaft under the action of a motor, At least one of a portion located in the range from the starting end of the nut in the axial direction to a position at least three times in the screw thread of the nut and a screw thread of the sliding screw shaft is formed of a diamond- ) Is formed on the surface of the substrate.

According to the electric actuator of the present invention, since the sliding screw shaft is made of a light metal or a light metal alloy, the load (inertial force) of the motor can be reduced. This makes it possible to construct the motor compact. In other words, the maximum transportable mass of the electric actuator can be increased without increasing the motor size (high output). Further, since the sliding screw shaft is used instead of the ball screw shaft, the nut can be downsized. Further, since the diamond-like carbon film is formed on at least one of the portion located at least three times from the starting end in the axial direction in the screw thread of the nut and the screw thread of the sliding screw shaft, It is possible to reduce the wear of the nut to improve the efficiency of the screw and to reduce the sliding noise of the sliding screw shaft and the nut. Therefore, wear resistance and durability of the sliding screw shaft and the nut can be improved, and the electric actuator can be made lighter, smaller, and noise-free.

In the electric actuator, the diamond-like carbon film may be formed at a portion located in a range from an axial end of a thread of the nut to at least three turns from an end of the nut. According to such a configuration, the abrasion of the sliding screw shaft and the nut can be further reduced.

In the electric actuator, the thickness of the diamond like carbon film at the first starting position located one turn from the starting end in the screw thread of the nut is preferably the thickness of the diamond at the second starting position located two turns from the starting end, It may be larger than the thickness of the like carbon film.

According to this structure, the thickness of the diamond-like carbon film at the first starting end portion of the nut is relatively large in the nut where the stress is liable to be concentrated at the time of driving the electric actuator, and the durability of the sliding screw shaft and the nut can be improved.

In the electric actuator, the thickness of the diamond-like carbon film of the first end portion located one turn from the end in the screw thread of the nut is preferably the thickness of the diamond of the second end portion located at the second position from the end, It may be larger than the thickness of the like carbon film.

According to this configuration, the thickness of the diamond-like carbon film at the first end portion of the nut is relatively large in the nut where the stress is liable to be concentrated at the time of driving the electric actuator, so that the durability of the sliding screw shaft and the nut can be further improved.

In the electric actuator, the diamond-like carbon film may be formed in a portion of the thread of the nut located at the displacement from the starting end to the ending end. According to this configuration, the efficiency of the screw can be further increased, and the sliding sound of the sliding screw shaft and the nut can be further suppressed.

Wherein the thickness of the diamond like carbon film in a region located in the range from the starting end of the nut to the third position from the end of the nut is in a range from the beginning and the fourth and subsequent positions from the terminating end, Like carbon film in the intermediate region located on the diamond-like carbon film.

According to such a configuration, since the thickness of the diamond-like carbon film at the starting end of the screw thread of the nut to which the stress acts at the time of driving the electric actuator and in the range from the end to the third wheel can be made comparatively large, The durability of the sliding screw shaft and the nut can be effectively improved.

In the electric actuator, the diamond-like carbon film may not be formed on at least a part of the intermediate region located in the range of the fourth and the following wheels from the beginning and the end in the screw thread of the nut.

According to such a configuration, it is possible to reduce the manufacturing cost of the electric actuator as compared with the case where the diamond-like carbon film is formed in the portion located in the range from the starting end to the terminating end in the screw thread of the nut.

In the electric actuator, the diamond-like carbon film may be formed on both the screw thread of the nut and the screw thread of the sliding screw shaft, the diamond-like carbon film being located at least three times from the starting end. According to this structure, the abrasion resistance of the sliding screw shaft and the nut can be further improved.

In the electric actuator, the sliding screw shaft is made of aluminum or an aluminum alloy, and an alumite film is formed on the screw thread of the sliding screw shaft and is located in a range from the starting end to the third winding position in the screw thread of the nut The diamond-like carbon film may be formed.

In the electric actuator, the nut may be composed of a light metal or a light metal alloy. With such a configuration, the load of the motor can be further reduced, so that the weight and size of the electric actuator can be further improved.

In the electric actuator, the diamond-like carbon film is formed on the screw thread of the sliding screw shaft, the nut is made of aluminum or an aluminum alloy, and an alumite film may be formed on the screw thread of the nut.

In the electric actuator, a diamond-like carbon film is formed on a screw thread of the sliding screw shaft, the nut is made of iron or an iron alloy, and a chromium film or a nickel film is formed on the screw thread of the nut It is possible.

In the electric actuator, the thickness of the diamond-like carbon film is preferably 0.1 μm or more and 6.0 μm or less. According to such a constitution, since the thickness of the diamond-like carbon film is not less than 0.1 mu m, the early peeling of the diamond-like carbon film due to abrasion can be appropriately suppressed. Further, since the diamond-like carbon film has a thickness of 6.0 m or less, the diamond-like carbon film can be reliably formed.

In the electric actuator, a gap space may be formed in the sliding screw shaft, in which the tip end of the screw thread of the nut and the sliding screw shaft are not in contact with each other and the tip end portion is disposed. According to such a configuration, even when the burr generated at the tip of the thread of the nut is not completely removed, the screw thread (DLC film) of the sliding screw shaft due to the bur can be prevented from being damaged.

In the electric actuator, the gap space may be formed so that the lubricant can be stored. With this configuration, since the lubricant can be efficiently supplied between the sliding screw shaft and the nut, the wear resistance and durability of the sliding screw shaft and the nut can be further improved, and furthermore, the electric actuator can be made to have a low noise level .

According to the present invention, since the diamond-like carbon film is formed on at least one of the portion located in the range of at least three turns from the starting end in the axial direction of the nut and the screw thread of the sliding screw shaft, It is possible to effectively improve the wear resistance and the durability of the light emitting device, and to achieve weight reduction, miniaturization, and low noise.

1 is a perspective view of an electric actuator according to a first embodiment of the present invention.
2 is an exploded perspective view of the electric actuator of FIG.
3 is a partial longitudinal cross-sectional view of the electric actuator of Fig.
4 is a partially enlarged view of the electric actuator of Fig.
5 is an enlarged vertical sectional view of the nut shown in Fig.
FIG. 6A is an enlarged longitudinal sectional view of the nut according to the first modification, and FIG. 6B is an enlarged vertical sectional view of the nut according to the second modification.
7 is a perspective view of an electric actuator according to a second embodiment of the present invention.
8 is an exploded perspective view of the electric actuator of Fig.
Fig. 9 is a partial longitudinal cross-sectional view of the electric actuator of Fig. 7;
10 is a partially enlarged sectional view of the electric actuator of Fig.
11 is an enlarged cross-sectional view of the sliding screw shaft and nut of Fig.
12 is a partially enlarged sectional view of Fig.

Hereinafter, preferred embodiments of the electric actuator according to the present invention will be described with reference to the accompanying drawings.

(First Embodiment)

1 to 3, an electric actuator 10 according to a first embodiment of the present invention includes a motor 12 as a rotation driving source, a rod cover 16 (not shown) provided through a housing 14 of the motor 12, A sliding screw shaft 18 for transmitting the rotational driving force of the motor 12 and a displacement portion 20 displaced in accordance with the rotation of the sliding screw shaft 18. 1 to 3, the right side (motor 12 side) of the sliding screw shaft 18 is referred to as the "base end" side, the left side of the sliding screw shaft 18 (side of the socket 56) Named.

The motor 12 may be constituted by a servo motor such as a brush DC motor, a brushless DC motor, a stepping motor, or the like.

 The housing 14 is formed in a circular shape and is fitted to the motor adapter 22 constituting the motor 12 from the outside. The rod cover 16 includes an elongated external cylinder 24 fitted outside from the housing 14 and an end block 26 provided at the tip of the external cylinder 24. [ The outer tube 24 is a tubular member formed in a cylindrical shape and provided therein with a rod 54, which will be described later, which constitutes the displacement portion 20. The end block 26 is formed in a rectangular shape when viewed from the front, and an insertion hole 30 through which the rod 54 is inserted is formed at the center thereof.

The sliding screw shaft 18 is connected to the motor shaft via a coupling 32. In the present embodiment, the coupling 32 may be omitted by making the sliding screw shaft 18 common to the motor shaft.

4, a bearing 34 is provided at the proximal end of the sliding screw shaft 18. As shown in Fig. The bearing 34 is, for example, a rolling bearing, but may be a sliding bearing.

The sliding screw shaft 18 is made of a light metal such as aluminum or a light metal alloy such as an aluminum alloy. Here, light metals are metals with a specific gravity of 4 or less. As described above, when the sliding screw shaft 18 is made of a light metal or a light metal alloy, the load of the motor 12 is reduced compared with the case where the sliding screw shaft 18 is made of a heavy metal such as iron (metal having a specific gravity larger than 4) And at the same time, the electric actuator 10 can be made lighter. A diamond-like carbon film (hereinafter referred to as a DLC film 50) is formed on the entire threaded portion 48 of the sliding screw shaft 18 (see FIG. 4).

 The DLC film 50 is an amorphous hard film made of a hydrocarbon or a carbon isotope and is excellent in lubricity, abrasion resistance, and resistance to seizure, and can be formed by CVD (Chemical Vapor Deposition) or PVD (Physical Vapor Deposition: Vapor growth) method. An intermediate layer between the substrate and the DLC film 50 may be formed in order to improve the adhesion between the DLC film 50 and the base material (screw thread 48 of the sliding screw shaft 18). The intermediate layer may be composed of, for example, a composite layer of a substrate and DLC. In this case, as the intermediate layer approaches the substrate, the composition ratio of the metal becomes larger while the composition ratio of the DLC becomes smaller and the metal composition ratio becomes smaller and the composition ratio of the DLC becomes larger as the distance from the substrate becomes smaller. By using such an intermediate layer, peeling of the DLC film 50 from the substrate is suitably suppressed.

The thickness of the DLC film 50 is set to preferably not less than 0.1 μm and not more than 6.0 μm, more preferably not less than 0.3 μm and not more than 4.0 μm, and more preferably not less than 0.5 μm and not more than 3.5 μm. If the thickness of the DLC film 50 is less than 0.1 mu m, there is a risk of premature peeling of the DLC film 50 due to abrasion. If the thickness of the DLC film 50 is larger than 6.0 mu m, And the peeling of the DLC film 50 easily occurs. It is also preferable that the thickness of the DLC film 50 is made larger than the surface roughness Rz (the interval between the surface irregularities) of the counterpart material (the DLC film 60 to be described later). This also applies to the DLC film 60.

The displaceable portion 20 includes a nut 52 screwed to the sliding screw shaft 18, a cylindrical rod 54 fixed to the nut 52 and passing through the insertion hole 30 of the end block 26, And a socket 56 mounted to close the distal opening of the rod 54.

The nut 52 is made of a light metal such as aluminum or a light metal alloy such as an aluminum alloy. According to this, the load of the motor 12 can be further reduced, and the electric actuator 10 can be made lighter. A DLC film 60 is formed on the entire threaded portion 58 of the nut 52 (see Fig. 5). The construction and the formation method of the DLC film 60 are the same as those of the DLC film 50 formed on the screw threads 48 of the sliding screw shaft 18, and therefore, detailed description thereof will be omitted.

5 of the screw thread 58 of the nut 52 is referred to as the " leading end ", the rightmost side (the end on the side of the motor 12) End) is referred to as " termination ", but it is natural that the positions of the starting end and the ending end may be reversed from left to right.

The thickness of the DLC film 60 in the portion (the first starting end portion 58a) located one turn from the starting end in the axial direction in the screw thread 58 (the screw thread 58 of the full thread portion) of the nut 52 (The second starting end portion 58b) located two turns from the starting end of the DLC film 60 is greater than the thickness of the DLC film 60. The thickness of the DLC film 60 at the second starting end portion 58b is larger than the thickness of the DLC film 60 at the third position from the starting end (the third starting end portion 58c).

The thickness of the DLC film 60 in the portion (the first end portion 58d) located one turn from the end in the axial direction of the threaded portion 58 of the nut 52 is set to be the same as the thickness Is greater than the thickness of the DLC film 60 of the second end portion 58e. The thickness of the DLC film 60 at the second end portion 58e is larger than the thickness of the DLC film 60 at the third portion (third end portion 58f) positioned three times from the end.

The thickness of the DLC film 60 at the third starting end portion 58c and the thickness of the DLC film 60 at the third end portion 58f are located four or more turns after the both ends in the screw thread 58 of the nut 52 (The middle portion 58g located between the third end portion 58c and the third end portion 58f) of the DLC film 60 is equal to or greater than the thickness of the DLC film 60. [

In this embodiment, the thickness of the DLC film 60 at the first end portion 58a and the first end portion 58d is set to 0.9 占 퐉, and the thickness of the second end portion 58b and the second end portion 58e The thickness of the DLC film 60 is set to 0.8 mu m and the thickness of the DLC film 60 of the third starting end portion 58c, the third terminating portion 58f and the middle portion 58g is set to 0.5 mu m. However, the thickness of the DLC film 60 formed on the screw thread 58 of the nut 52 can be arbitrarily set.

The electric actuator 10 according to the present embodiment is basically configured as described above, and its operation and operation effects will be described next. 1 and 3, the state in which the rod 54 is housed inside the outer cylinder 24 will be described as an initial position.

In this initial position, when the motor shaft is rotationally driven by supplying current to the motor 12 from a power source not shown, the rotational power of the motor shaft is transmitted to the sliding screw shaft 18 via the coupling 32 do. When the sliding screw shaft 18 is rotated, the rod 54 and the socket 56 together with the nut 52 are displaced toward the leading end side (opposite to the motor 12). At this time, stress is concentrated on the first to third end portions 58a to 58c of the thread 52 of the nut 52, but the DLC film 60 is formed on the first to third start portions 58a to 58c The DLC film 50 is formed on the entire threaded portion 48 of the sliding screw shaft 18 so that the nut 52 is smoothly displaced toward the front end along the axial direction of the sliding screw shaft 18 It becomes possible.

On the other hand, when the rod 54 is to be returned to the initial position, the motor shaft is driven to rotate in the direction opposite to the above. In this way, the rotational power of the motor shaft is transmitted to the sliding screw shaft 18 via the coupling 32. The rod 54 and the socket 56 together with the nut 52 are displaced toward the base end side (the motor 12 side) by the rotation of the sliding screw shaft 18 in the opposite direction. Stress is concentrated on the first to third end portions 58d to 58f of the screw thread 58 of the nut 52 but the DLC film 60 is formed on the first to third end portions 58d to 58f The nut 52 is smoothly displaced toward the base end along the axial direction of the slidable screw shaft 18 because the DLC film 50 is formed on the entire threaded portion 48 of the slidable screw shaft 18 It is possible.

According to the present embodiment, since the sliding screw shaft 18 is made of a light metal or a light metal alloy, the load (inertial force) of the motor 12 can be reduced. By doing so, the motor 12 can be configured compactly. In other words, the maximum transportable mass of the electric actuator 10 can be increased without increasing the size (high output) of the motor 12. [

In addition, by using the sliding screw shaft 18 instead of the ball screw shaft, the nut 52 can be downsized. The DLC film 60 is formed on the threaded portion 58 of the nut 52 in the range from the beginning to the end and the DLC film 50 is attached to the threaded portion 48 of the sliding screw shaft 18, It is possible to improve the efficiency of the screw (the ratio of the screw output to the screw input) by reducing the wear of the sliding screw shaft 18 and the nut 52, (52) Sliding sound can be reduced. Therefore, wear resistance and durability of the sliding screw shaft 18 and the nut 52 can be improved, and the electric actuator 10 can be made lighter, smaller, and noise-free.

The thickness of the DLC film 60 at the first starting end portion 58a in the screw thread 58 of the nut 52 is set to be larger than the thickness of the DLC film 60 at the second starting end portion 58b, The thickness of the DLC film 60 at the end portion 58d is made larger than the thickness of the DLC film 60 at the second end portion 58e. The thickness of the DLC film 60 in the first end portion 58a and the first end portion 58d in which stress is liable to be concentrated at the time of driving the electric actuator 10 is made relatively large, And the nut 52 can be improved in durability.

The thickness of the DLC film 60 of the first to third end portions 58a to 58c and the first to third end portions 58d to 58f is not less than the thickness of the DLC film 60 of the middle portion 58g , The sliding screw shaft 18 and the nut 52 can be efficiently improved.

In the present embodiment, since the nut 52 is made of a light metal or a light metal alloy, the load on the motor 12 can be further reduced. This makes it possible to reduce the weight and size of the electric actuator 10.

Further, since the thickness of the DLC films 50 and 60 is 0.1 m or more, the early delamination of the DLC films 50 and 60 due to abrasion can be suitably minimized. Further, since the thickness of the DLC films 50 and 60 is 6.0 占 퐉 or less, the DLC films 50 and 60 can be reliably formed.

The electric actuator 10 according to the present embodiment is not limited to the above-described configuration. The sliding screw shaft 18 is made of an alloy of a light metal or a light metal and a portion located in the range from the starting end portion in the axial direction of the screw thread 58 of the nut 52 to the third And the screw threads 48 of the sliding screw shaft 18 may be formed on at least one of the DLC films 50 and 60. That is, in this embodiment, for example, a combination of the sliding screw shaft 18 and the nut 52 shown in Table 1 can be adopted.

Sliding screw shaft nut Constituent material film Constituent material film One Light or light alloy DLC Light or light alloy DLC 2 Light or light alloy DLC Aluminum or
Aluminum alloy Alumite 3 Aluminum or
Aluminum alloy Alumite Light or light alloy DLC 4 Light metal or
Light metal alloy DLC Copper or copper alloy DLC 5 Aluminum or
Aluminum alloy Alumite Copper or copper alloy DLC 6 Light or light alloy DLC Iron or iron alloy DLC 7 Light or light alloy DLC Iron or iron alloy Hard chrome 8 Light or light alloy DLC Iron or iron alloy nickel 9 Aluminum or
Aluminum alloy Alumite Iron or iron alloy DLC

 6A, when the DLC film 60 is formed on the screw thread 58 of the nut 52, at least a portion of the intermediate portion 58g (all in FIG. 6A) The DLC film 60 may be formed on the first to third end portions 58a to 58c and the first to third end portions 58d to 58f without forming the DLC film 60 on the first to third end portions 58a to 58c. 6B, the DLC film 60 may not be formed on the first to third end portions 58d to 58f and the intermediate portion 58g, but the first to third start portions 58d to 58d may be formed without forming the DLC film 60 on the first to third end portions 58d to 58f and the middle portion 58g. The DLC film 60 may be formed on the first and second electrodes 58a to 58c. 6A and 6B, the manufacturing cost of the electric actuator 10 can be further reduced.

(Second Embodiment)

 Next, an electric actuator 10A according to a second embodiment of the present invention will be described with reference to Figs. 7 to 12. Fig. In the electric actuator 10A according to the second embodiment, the same components as those of the electric actuator 10 according to the first embodiment described above are denoted by the same reference numerals, and a detailed description thereof will be omitted.

7 to 10, the electric actuator 10A according to the present embodiment includes a motor 12 as a rotation drive source, a base portion 100 provided to the motor 12 via the housing 14, (Feed screw shaft) 102 for transmitting the rotational driving force of the slide screw shaft 12, and a displacement portion 104 displaced in accordance with the rotation of the sliding screw shaft 102.

The base portion 100 includes a base portion main body 106 having a U-shaped cross section extending in the axial direction of the sliding screw shaft 102, 1 end plate 108 and a second end plate 110 formed at the front end of the base body 106 (the end opposite to the motor 12). Each of the first end plate 108 and the second end plate 110 is fixed to the base portion main body 106 by a plurality of fixing screws 112.

That is, a space S is formed in the base portion 100, in which the displacement portion 104 is provided by the base portion main body 106, the first end plate 108, and the second end plate 110 . The base portion main body 106 is formed with an opening 114 communicating with the space S over its entire length. The opening 114 is covered with a plate-like lid 116. This prevents dust from entering the space S from the outside of the base portion 100 through the opening portion 114. [ The lid portion 116 is fixed to the first end plate 108 and the second end plate 110 by a fixing screw 118.

The first end plate 108 is formed with a through hole 120 through which the sliding screw shaft 102 is inserted so that the housing 14 is fitted inward. The second end plate 110 is provided with an oil hole 122 for supplying grease to the sliding screw shaft 102 and a later-described grease reservoir 152.

The sliding screw shaft 102 has its proximal end supported in the axial direction by a rolling bearing 124 provided in the housing 14 and its distal end supported by a sliding bearing 126 provided on the second end plate 110 And is supported in the axial direction. The sliding screw shaft 102 is made of a light metal such as aluminum or a light metal alloy such as an aluminum alloy and the DLC film 130 is formed on the entire screw thread 128 of the sliding screw shaft 102. The DLC film 130 may be formed in the same manner as the DLC film 50 described above (see FIG. 11).

The displaceable portion 104 includes a displacement body 132 in the shape of a block (cuboid) provided in the space S of the base portion 100, A neck portion 134 extending from the neck portion 132, a table 136 provided on the neck portion 134, and a nut 138 screwed to the sliding screw shaft 102 in the state of being provided in the displacing portion main body 132 ).

A plurality of guide pins 140 are provided on both sides of the displacing portion main body 132 to slide on the inner surface of the base portion main body 106 extending in the axial direction of the sliding screw shaft 102. The guide pin 140 includes a first stopper 142 fixed to the base end face of the displacing portion main body 132 and a second stopper 144 fixed to the front end face of the displacing portion main body 132, 132 in the axial direction of the sliding screw shaft 102. [ A communicating hole 146 is formed in the second stopper 144 at a position opposite to the oil supply hole 122 of the second end plate 110.

A nut-positioning hole 148 having a circular shape is provided with a nut 138 in the displaceable portion main body 132. In the nut placement hole 148, a circular ring cap 150 is provided on the side of the first stopper 142 rather than the nut 138. The cap 150 is fixed to the wall constituting the nut arrangement hole 148, and the sliding screw shaft 102 is inserted into the cavity of the cap 150. That is, a grease reservoir 152 is formed between the nut 138 and the cap 150 to introduce grease between the nut 138 and the sliding screw shaft 102.

10, a through hole 154 communicating with the communication hole 146 of the second stopper 144 extending through the entire length, a through hole 154 communicating with the communication hole 146 of the second stopper 144, And an introduction hole 156 communicating with the grease reservoir 152 are formed. The through hole 154 is provided with a packing (closing member) 158 provided to close the opening of the first stopper 142 side. It is possible to suppress leakage of grease from between the displacing portion main body 132 and the first stopper 142 by the packing 158. [

The table 136 is formed to have a wider width than the displacing portion main body 132. [ The table 136 is formed with an insertion hole 160 through which the cover portion 116 is inserted. Thereby, when the displacement portion 104 is displaced with respect to the base portion 100, the displacement portion 104 and the cover portion 116 do not interfere with each other. The table 136 is provided with a plurality of mounting holes 162 for mounting unshown work or the like.

The nut 138 is formed in a cylindrical shape and is displaced in the axial direction in accordance with the rotation of the sliding screw shaft 102. The nut 138 is fixed to the displacing portion main body 132 by a pin 164 and a detent screw 166 while being provided in the nut arranging hole 148. The nut 138 is made of a light metal such as aluminum or a light metal alloy such as an aluminum alloy and the DLC film 170 is formed on the threaded portion 168 of the nut 138 as shown in Fig. have. The DLC film 170 is formed in the same manner as the DLC film 60 described above.

That is, the thickness of the DLC film 170 of the first starting end portion 168a in the screw thread 168 of the nut 138 is larger than the thickness of the DLC film 170 of the second starting end portion 168b in the screw thread 168 of the nut 138 170) thickness. The thickness of the DLC film 170 at the second starting end portion 168b is larger than the thickness of the DLC film 170 at the third starting end portion 168c in the screw thread 168 of the nut 138. [

The thickness of the DLC film 170 at the first end portion 168d of the screw thread 168 of the nut 138 is greater than the thickness of the DLC film 170 at the second end portion 168e of the screw thread 168 of the nut 138. [ Is greater than the thickness. The thickness of the DLC film 170 at the second end portion 168e is greater than the thickness of the DLC film 170 at the third end portion 168f of the screw thread 168 of the nut 138. [

The thickness of the DLC film 170 at the third starting end portion 168c and the thickness of the DLC film 170 at the third end portion 168f are set such that the DLC film 170 of the middle portion 168g of the screw thread 168 of the nut 138, (170) thick or more.

As shown in Fig. 12, the screw thread 168 of the nut 138 is formed such that its cross-sectional shape along the axial direction of the sliding screw shaft 102 on its upper surface is flat. Generally, a burr due to cutting tends to be generated at the tip corner 171 of the screw thread 168 of the nut 138. These burrs can be removed by shot blasting or chemical polishing, but it is not easy to visually confirm burr removal. When the burr remains on the tip corner 171 of the screw thread 168 of the nut 138, the DLC film 130 of the screw thread 128 of the sliding screw shaft 102 by this burr There is a possibility of being damaged.

In this embodiment, in order to prevent the DLC film 130 of the sliding screw shaft 102 from being damaged, the bottom end of the sliding screw shaft 102 is provided with a groove (Tip end) 171 is provided on the outer circumferential surface. Specifically, the wall surface constituting the gap space 172 has a curved surface 174 having a semicircular cross-sectional shape along the axial direction of the sliding screw shaft 102, a curved surface 174 having a curved surface 174 in the axial direction of the sliding screw shaft 102, And a pair of planes 176 connected to both sides of the plane 174.

The pair of planes 176 extend from the crest of the nut 138 to the bottom of the valley a little less than the crest of the nut 138 in a state of being tilted away from each other in a direction away from the curved surface 174. An acute angle? 1 formed by each plane 176 and a straight line perpendicular to the axis of the sliding screw shaft 102 is smaller than a flank angle? 2 of the nut 138. Each of the flat surfaces 176 (the slidable screw shaft 102) is in contact with the leading edge corner (not shown) of the screw thread 168 of the nut 138 with the slidable screw shaft 102 and the nut 138 threadedly engaged 171). The DLC film 130 of the screw thread 128 of the sliding screw shaft 102 can not be removed even if burrs generated at the tip corner 171 of the screw thread 168 of the nut 138 are not completely removed. It is prevented from being damaged by burrs. In addition, when the DLC film 130 is not formed on the screw threads 128 of the sliding screw shaft 102, the screw thread 128 of the sliding screw shaft 102 can be prevented from being damaged.

The gap space 172 also functions as a grease holding space for holding the grease introduced from the grease reservoir 152. That is, the gap space 172 is formed so that grease (lubricant) can be stored. As a result, grease can be effectively supplied between the sliding screw shaft 102 and the nut 138, so that the wear resistance and durability of the sliding screw shaft 102 and the nut 138 can be further improved, It is possible to further reduce the noise of the battery 10A.

Further, in the present embodiment, it is possible to easily supply grease to the grease reservoir 152 when the amount of grease in the grease reservoir 152 is insufficient. That is, when grease is supplied, the displaceable portion 104 is moved toward the front end with respect to the sliding screw shaft 102.

The second stopper 144 comes into contact with the second end plate 110 so that the feed hole 122 of the second end plate 110 and the communication hole 146 of the second stopper 144 communicate with each other. In other words, the oil hole 122 is communicated with the grease reservoir 152 via the communication hole 146, the through hole 154, and the introduction hole 156. At this time, leakage of grease from between the displacing portion main body 132 and the first stopper 142 is suppressed by the action of the packing 158. In this state, grease is injected from the oil holes 122 and supplied to the grease reservoir 152. The grease supplied to the grease reservoir 152 is introduced between the nut 138 and the sliding screw shaft 102 by displacing the displacement portion 104 toward the base end with respect to the sliding screw shaft 102. [

The electric actuator 10A according to the present embodiment achieves the same operational effects as the electric actuator 10 according to the first embodiment described above.

The electric actuator 10A of the present embodiment is not limited to the above-described configuration. In the present embodiment, for example, a combination of the sliding screw shaft 102 and the nut 13 shown in Table 1 above may be employed. When the DLC film 170 is formed on the threaded portion 168 of the nut 138, the DLC film 170 is not formed on at least a part of the intermediate portion 168g and the first to third leading end portions 168a And the DLC film 170 may be formed on the first to third end portions 168d to 168f. The DLC film 170 is not formed on the first to third end portions 168d to 168f and the intermediate portion 168g and the DLC film 170 is formed on the first to third start portions 168a to 168c May be formed. In this case, it is possible to further reduce the manufacturing cost of the electric actuator 10A.

It is needless to say that the electric actuator according to the present invention is not limited to the above-described embodiment, and various configurations can be adopted without departing from the gist of the present invention.

Claims (15)

Nuts (52, 138) threadably engaged with the sliding screw shaft (18, 102) by rotating the sliding screw shaft (18, 102) under the action of the motor (12) In the electric actuator (10, 10A) displaced along the axial direction,
The sliding screw shafts 18 and 102 are made of a light metal or a light metal alloy,
A portion of the screw threads 58 and 168 of the nuts 52 and 138 located in the range from the starting end in the axial direction to at least three turns and the screw threads 48 and 128 of the sliding screw shafts 18 and 102, (10, 10A), wherein diamond-like carbon films (50, 60, 130, 170) are formed on at least one of the first and second surfaces. The diamond-like carbon film (60, 170) is provided on a portion of the screw threads (58, 168) of the nuts (52, 138) (10, 10A). The diamond-like carbon film (60, 170) of the first starting end portion (58a, 168a) located one turn from the starting end in the screw threads (58, 168) of the nuts (52, 138) Wherein the thickness of the diamond like carbon film (60, 170) of the second starting portion (58b, 168b) located two turns from the starting end is larger than the thickness of the diamond like carbon film (60, 170). The diamond-like carbon film (60, 170) of the first end portion (58d, 168d) located one turn from the end of the screw threads (58, 168) of the nut (52, 138) Wherein the thickness is larger than the thickness of the diamond-like carbon film (60, 170) of the second end portion (58e, 168e) located two turns from the end. The diamond-like carbon film (60, 168) as set forth in any one of claims 2 to 4, wherein the diamond-like carbon film (60, 170) are formed on the outer circumferential surface. The diamond-like carbon film (60, 170) as set forth in claim 5, wherein a thickness of the diamond-like carbon film (60, 170) in a range of the screw threads (58, 168) Is greater than or equal to the thickness of the diamond-like carbon films (60, 170) of the intermediate portions (58g, 168g) located at the starting end and the fourth wheel or more from the end. The tool according to claim 2, wherein at least a part of the intermediate portions (58g, 168g) located in the fourth and subsequent ranks from the starting end and the ending end in the thread threads (58, 168) of the nuts (52, 138) Like carbon films (60, 170) are not formed. The screw thread according to any one of claims 1 to 5, wherein the screw threads (58, 168) of the nuts (52, 138) Wherein the diamond-like carbon films (50, 60, 130, 170) are formed on both of the first, second, third, [2] The apparatus according to claim 1, wherein the sliding screw shafts (18, 102) are made of aluminum or an aluminum alloy,
An alumite film is formed on the screw threads (48, 128) of the sliding screw shaft (18, 102)
Like carbon film (60, 170) is formed in a portion of the screw threads (58, 168) of the nuts (52, 138) (10, 10A). The electrical actuator (10, 10A) according to claim 8 or 9, characterized in that the nuts (52, 138) are made of a light metal or a light metal alloy. Like carbon films (50, 130) are formed on the screw threads (48, 128) of the sliding screw shaft (18, 102), and the nuts (52, 138) , And an alumite film is formed on the threads (58, 168) of the nuts (52, 138). The diamond-like carbon film (50, 130) is formed on the screw threads (48, 128) of the sliding screw shaft (18, 102) , Wherein the screw threads (58, 168) of the nuts (52, 138) are formed with a chromium film or a nickel film. The electric actuator (10, 10A) according to any one of claims 1 to 12, wherein the thickness of the diamond-like carbon film (50, 60, 130, 170) is 0.1 μm or more and 6.0 μm or less. The slide fastener according to any one of claims 1 to 13, wherein the tip end portion (171) of the screw thread (168) of the nut (138) and the slide screw shaft (102) , And a gap space (172) in which the tip end (171) is disposed is formed. The electric actuator (10A) according to claim 14, characterized in that the gap space (172) is formed so that lubricant can be stored.

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